This invention relates generally to plastic closure cap constructions, and more particularly to devices of this type which provide a visual indication if unauthorized use of or tampering with the container has occurred.
In the recent past, a number of different tamper-resistant/tamper-evident closure constructions have been proposed and produced. U.S. Pat. No. 4,291,813 shows one arrangement, illustrating a dispenser employing a retainer ring on a screw cap, the ring being pivotally connected to the cap along a thin annular line of weakness and being capable of forced movement over a cooperable lip on the neck of a container. Following assembly at the facility where the product is being filled, the cap is installed on the container and at the same time the ring shifted downwardly over the container lip, thereby retaining the cap against unauthorized removal. Upon initial use of the dispenser the cap, being unscrewed, causes the ring to separate along the line of weakness. In this particular construction, the ring is intended to remain with the container following removal of the cap.
Yet another construction is illustrated in U.S. Pat. No. 3,650,428, involving a dispenser having external ratchet teeth disposed on the exterior surface of the neck of a container. These teeth cooperate with internal teeth on a locking ring which is carried by the closure cap. The connection between the latter and ring is in the form of multiple frangible webs that remain intact prior to initial use of the dispenser, but which are ruptured when the cap is first unscrewed.
Other arrangements involving tamper-evident closures are illustrated in U.S. Pat. Nos. 4,156,490; 4,299,328 and 3,348,718. In U.S. Pat. No. '490, the retainer ring is provided with internal left-hand threads which, during unscrewing of the cap, operate to force the ring in an axially downward direction, thereby enhancing the tensile break-away force applied to the webs that connect the cap to the ring. U.S. Pat. No. '328 shows a somewhat similar dispenser having a screw cap connected to a retainer band by a series of thin webs which are intended to break away during initial use. U.S. Pat. No. '718 involves a metal closure for a bottle, wherein a relatively thin shell is placed over the container neck and thereafter a crimping operation performed which imparts threads to the cap, and at the same time creates a shoulder in a part that fits under a cooperable external shoulder in the neck of the container. The upper and lower portions of the closure break apart when the upper portion is initially unscrewed.
In all of the above patents, breakage or rupturing of the ribs provides the desired visual indication to the user that the device may have been previously opened or otherwise tampered with in an unauthorized manner; in such cases the purity of the product is subject to question, as is its freshness. These considerations are especially important where foods or medicines are involved, as can be readily appreciated.
While many of the prior tamper-proof containers have met with varying degrees of success and have performed their intended functions reasonably well, it has still been necessary for the consumer to be especially circumspect as far as making close examination of the tamper-proof structures. That is, where thin webs have been employed in the past, their breakage has sometimes gone unnoticed unless it was accompanied by a substantial tear or deformation of the surrounding structure of the cap. In addition, some of the prior arrangements were relatively expensive to manufacture, and difficult to reproduce in large quantities and within the tolerances required in order to yield acceptable operation.